/*
 * Created on 09-Sep-2004
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.core3.util;

import java.nio.ByteBuffer;

/**
 * @author parg
 * 
 */

public class ConcurrentHasherRequest {
    private static AEMonitor class_mon = new AEMonitor("ConcHashRequest:class");

    private ConcurrentHasher concurrent_hasher;
    private ByteBuffer buffer;
    private ConcurrentHasherRequestListener listener;

    private int size;
    private byte[] result;
    private boolean cancelled;
    private boolean low_priority;

    private AESemaphore sem = new AESemaphore("ConcHashRequest");

    protected ConcurrentHasherRequest(ConcurrentHasher _concurrent_hasher, ByteBuffer _buffer, ConcurrentHasherRequestListener _listener,
            boolean _low_priorty) {
        concurrent_hasher = _concurrent_hasher;
        buffer = _buffer;
        listener = _listener;
        low_priority = _low_priorty;

        size = buffer.limit() - buffer.position();
    }

    /**
     * synchronously get the result of the hash - null returned if it is cancelled
     * 
     * @return
     */

    public byte[] getResult() {
        sem.reserve();

        return (result);
    }

    /**
     * cancel the hash request. If it is cancelled before it is completed then a subsequent call to getResult will return null
     */

    public void cancel() {
        if (!cancelled) {

            cancelled = true;

            sem.releaseForever();

            ConcurrentHasherRequestListener listener_copy;

            try {
                class_mon.enter();

                listener_copy = listener;

                listener = null;

            } finally {

                class_mon.exit();
            }

            if (listener_copy != null) {

                listener_copy.complete(this);
            }
        }
    }

    public boolean getCancelled() {
        return (cancelled);
    }

    public int getSize() {
        return (size);
    }

    public boolean isLowPriority() {
        return (low_priority);
    }

    protected void run(SHA1Hasher hasher) {
        if (!cancelled) {

            if (AEDiagnostics.ALWAYS_PASS_HASH_CHECKS) {

                result = new byte[0];

            } else {

                result = hasher.calculateHash(buffer);
            }

            sem.releaseForever();

            if (!cancelled) {

                ConcurrentHasherRequestListener listener_copy;

                try {
                    class_mon.enter();

                    listener_copy = listener;

                    listener = null;

                } finally {

                    class_mon.exit();
                }

                if (listener_copy != null) {

                    listener_copy.complete(this);
                }
            }
        }
    }
}
